Abandonment, neglect, sexual abuse, and even what triggers an individual’s death can be unwrapped by just studying the biology and reproductive behaviour of human lice.

Researchers from the University of Reading (UK) and the University of Pavia (Italy) have studied head lice populations in severe and regular infestations.  With access to data of hairs with head lice and especially nits, it is possible to estimate not only for how long a victim has been exposed to neglect, but also how frequently.  Based on the analysis of a serious case of a victim of neglect who died shortly after being admitted to hospital, lice reproductive biology enabled the interpretation of the cause of death, and revealing for how long she was overdosing on medication.

The victim had a very heavy head louse infestation.  A number of hairs were analysed for the occurrence of nits.  Female lice were also studied.  All hairs were almost totally covered with groups of mainly 2 and 3 nits.  The overall distribution of grouped nits allowed an estimation of ca. 2 years of constant neglect or abandonment.  In the distal (older) tip of hairs there were scattered groups of nits, suggesting repeated and early exposure to neglect, that culminated in the prolonged ~2 years massive infestation.  Nits forming clusters is common in body lice, not in head lice, and the study revealed that head lice nits forming groups is a clear marker of neglect.  In severe infestations, females run out of space to lay eggs, resulting in overlapping attachment sites

Head lice egg (bar 1mm)
Female head louse (approx. length 2.3 mm)
Male head louse (approx. length 2.2 mm)

But what explained the cause of death were two clues only offered by head lice.  One, there were no nits within 1.5 to 2cm of the proximal end of the hairs, near the scalp.  Because head lice lay eggs at 0.5cm of the scalp, this gap with no nits close to the scalp, despite the thousands of adults crawling on the head, was totally unexpected.  Two, female lice had their embryos dying inside their bodies, and were unable to deliver any eggs.  These two facts were indicative of something in the blood of the victim that was intoxicating both lice and victim.  During the period of neglect, the elder was taking nifedipine – a medicine to control high blood pressure. The active compound of nifedipine is a powerful Calcium Channel Blocker (CCB), that in excess stops embryo development, in mammals as in insects.  The medication stops lice reproduction if they feed on blood with high enough CCB doses.  The hair’s gap of nits 1.5 to 2 cm from the scalp suggests up to 2 months of overdosing of the medication, in other words, estimating the moment it started.

Humans carry head, body and pubic lice; and the three can offer their biology to interpret what has happened to a victim in a number of circumstances.  Pubic lice are unable to crawl on scalp hair, because these hairs are too thin.  In children or toddlers, the only thick enough hairs available are the eyelashes and the eyebrows (no pubic hairs have grown yet).  For example, nits in eyebrows or eyelashes of toddlers or children mean sexual abuse, a serious crime that goes under-reported time and time again, because the nits of the three lice varieties look similar to the untrained eye.

A single page form is included in the article, to be used by practitioners, doctors, nurses, teachers and family members, to record lice infestations -this data can facilitate unravelling neglect, abandonment and abuse before it is too late.

The paper  ‘Using human head lice to unravel neglect and cause of death’ , published in  Parasitology, is available free for one month.

 

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